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Remove code intended for Go 1.4 and older.

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This change only removes optimizations for older Go releases that we
no longer support in the internal/zero package.  This package should
still continue to build on older releases.
This commit is contained in:
Josh Rickmar 2016-04-28 09:50:20 -04:00
parent b97d824975
commit 42593c7dfd
2 changed files with 1 additions and 54 deletions
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5
internal/zero/slice.go
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@ -3,10 +3,7 @@
// license that can be found in the LICENSE file.
// This file implements range-based zeroing, which as of Go 1.5 is
// optimized using a Duff's device. See slice14.go for an implementation
// optimized for previous Go versions.
//
// +build !go1.3,!go1.4
// optimized using a Duff's device.
package zero

50
internal/zero/slice14.go
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@ -1,50 +0,0 @@
// Copyright (c) 2015 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
// Go >= 1.5 optimizes range-based zeroing of the form:
//
// for i := range slice {
// slice[i] = 0
// }
//
// to an optimized implementation using a Duff's device, but older versions
// do not and benefit from this custom implementation.
//
// +build go1.3 go1.4
package zero
import (
"math/big"
)
// Bytes sets all bytes in the passed slice to zero. This is used to
// explicitly clear private key material from memory.
//
// In general, prefer to use the fixed-sized zeroing functions (Bytea*)
// when zeroing bytes as they are much more efficient than the variable
// sized zeroing func Bytes.
func Bytes(b []byte) {
z := [32]byte{}
n := uint(copy(b, z[:]))
for n < uint(len(b)) {
copy(b[n:], b[:n])
n <<= 1
}
}
// BigInt sets all bytes in the passed big int to zero and then sets the
// value to 0. This differs from simply setting the value in that it
// specifically clears the underlying bytes whereas simply setting the value
// does not. This is mostly useful to forcefully clear private keys.
func BigInt(x *big.Int) {
b := x.Bits()
z := [16]big.Word{}
n := uint(copy(b, z[:]))
for n < uint(len(b)) {
copy(b[n:], b[:n])
n <<= 1
}
x.SetInt64(0)
}